Automatic selecting switches as used in automatic telephone systems



Feb. 20, 1962 J. D. LESLIE 3,022,388

AUTOMATIC SELECTING SWITCHES AS USED IN AUTOMATIC TELEPHONE SYSTEMSFiled Aug. 11, 1959 INV'ENTOR JOHN DOUGLAS LESLIE 3,022,388 AUTGMATICSELECTING SWITiII-IES AS USED IN AUTOMATIC TELEPHONE SYSTEMS JohnDouglas Leslie, London, England, assignor to themens Edison SwanLimited, London, England, a British company Filed Aug. 11, 1959, Ser.No. 832,927 Claims priority, application Great Britain Aug. 19, 1958 1Claim. (Cl. 200-11) This invention relates to automatic selectingswitches of the type used in automatic telephone systems and in whichwipers wipe over fixed contacts, termed bank con tacts, mounted toconstitute a so-called contact bank.

It is well known to employ, in an automatic selecting switch of the typereferred to, a form of contact bank which comprises a plurality ofmoulded bank units clamped together, each moulded bank unit comprisingone or two rows of bank contacts moulded into insulating material. Ingeneral, known moulded bank units are such that the track wiped by aWiper traversing a row of bank contacts is of a mechanically brokennature, the mechanically broken nature of the track being due to thefact that the wiped portions of the bank contacts are tip portions thatprotrude in cantilever fashion from, and quite clear of, the insulatingmaterial in which the bank contacts are moulded, so that the track isinterrupted mechanically, as well as electrically, in the gaps betweenbank contacts of the row, Disadvantages of such a track are that itsmechanically broken nature tends to increase the incidence of troublesdue to wiper vibration or bounce and to increase the mechanical loadonthe driving means of the switch.

With bank contacts and contact banks of the forms and sizes usuallyemployed, a difficulty is encountered if it is attempted to avoid thedisadvantage just mentioned by arranging that the insulating material ofa moulded bank unit extends, in the form of small portions or tonguesprotruding from the main body of this material, into the gaps betweenbank contacts of a row so that these gaps are filled with insulatingmaterial flush with the contact ing surfaces of these bank contacts.This difficulty is the practical one that the small protruding portionsor tongues of insulating material are too fragile or too readilydisplaced to be satisfactory. Y

The present invention provides an improved moulded bank unit which issuch that the track wiped by a wiper traversing a rowof bank contacts isa smooth and me,- chanically unbroken one, and in which the difficultyreferred to is fully overcome.

According to the main feature of the invention there is provided amoulded bank unit, comprising bank con tacts moulded into insulatingmaterial, wherein each of a plurality of bank contacts forming a row hasa tag por tion which protrudes clear of the moulded insulating materialfrom a face of a main body of this material, an embedded portion whichis embedded in the main body of the moulded insulating material so thatnone of its surface is exposed, and a wiped portion Which protrudes froma further face of the main body of the moulded insulating material andwhich has its surface partly exposed to permit of requisite wiperengagement with it, and wherein the moulded insulating material soextends, in the form of strips protruding from the main body of thismaterial, into the gaps between said wiped portions of the bankcontacts, of the'row that these gaps are filled with insulating materialflush with the contacting surfaces of said wiped portions to provide atleast one smooth and mechanically unbroken wiper track, and wherein saidstrips are supported, at their ends remote from the main body of themoulded insulating material, by a sup porting portion of the mouldedinsulating material, this nite States atent supporting portiontaking-the form of a continuous length of the moulded insulatingmaterial integral with said main body and with said strips andinterconnecting said ends of said strips. It is contemplated that hardnylon may be employed as the insulating material.

According to a subordinate feature of the invention, in a moulded bankunit as just set forth each of the bank contacts forming the row has, inaddition to the tag and embedded and wiped portions referred to, afurther portion which is embedded in said supporting portion of themoulded insulating material, it being thereby arranged that thissupporting portion is itself supported mainly by said bank contacts.

In order that the invention may be more readily and fully understood, aspecific embodiment of it will now be described by way of example withreference to the accompanying drawing. This embodiment takes the form ofa moulded bank unit for use in building up the contact bank of aselecting switch of the rotary uniselector type. Fig. 1 of the drawingshows a plan view of the bank unit, FIG. 2 shows (on a larger scale thanFIG. 1) a view in isometric projection of a portion of the bank unit,and FIG. 3 shows a somewhat diagrammatic view illustrating how acomposite. wiper cooperates with such a bank unit in a contact bankcomprising a plurality of such bank units. FIGS. 4, 5, and 6 illustratethe preferred form of the contacting tip of a constituent wiper used informing a composite wiper as just referred to, FIG. 4 being a plan viewof the tip portion of the constituent wiper and FIGS. 5 and 6 being sideand end views respectively.

Referring firstly to FIGS. 1 and 2, the moulded bank unit concernedcomprises a single row of bank contacts 1 moulded into a unitary mass ofinsulating material 2. Each bank contact has the general form of a thinconducting metal strip, and the bank contacts as a whole are arranged inthe well-known manner so that they lie in the same plane and are radialwith respect to an axis. The main body 3 of the moulded insulatingmaterial has two major plane faces, such as the face 4, each having twoedges which are radial with respect to said axis and two edges which arearcuate with respect to said axis, and has two minor plane faces, suchas the face 5, which are end faces and are rectangular, and has a curvedouter face (not seen in the figures) and a curved inner face 6. Eachbank contact 1 has a tag portion 7 which protrudes from said curvedouter face, an embedded portion 8 (see FIG. 1) which is embedded in themain body 3 of the moulded insulating material so that none of itssurface is exposed, a wiped portion 9 which protrudes from said curvedinner face and has its two major surfaces (i.e. the surfaces other thanits two thin edges) exposed to permit of wiper engagement with them, afurther portion it? (see FIG. 1) which is embedded in a supportingportion it of the moulded insulating material, and a still furtherportion 12 which protrudes from said supporting portion of the mouldedinsulating material. Strips 13 of the moulded insulating materialprotrude from the main body 3 of this material to fill the gaps betweensaid wiped portions 9 of the bank contacts to provide two smooth andmechanically unbroken wiper tracks, one facing in the same direction asone of the two major plane faces of the main body of the mouldedinsulating material and the other facing in the opposite direction. Eachof these two tracks is arcuate with respect to said axis and includesone of the exposed (contacting) major surfaces of said wiped portion 9of each bank contact. Said supporting portion 11 of the mouldedinsulating material takes the form of a continuous arcuate length ofinsulating material which is of rounded cross-section, and which isintegral with the main body 3 of the moulded insulating material and theprotruding strips 13 of this material and interconnects the ends ofthese strips remote from said main body, and which serves to support theprotruding strips at said ends. The supporting portion 11 of the mouldedinsulating material is itself supported mainly by the bank contacts. Thecross-sectional dimesnion of said supporting portion 11 parallel to saidaxis is considerably less than the distance 'between the major faces ofthe main body 3 of the moulded insulating material. The holes 29 in themain body 3 of the moulded insulating material serve to accommodate theclamping bolts employed in clamping a plurality of such moulded bankunits together to form a contact bank. The unit is intended for use witha composite wiper of the kind cornprising in effect two constituentWipers which are electrically connected together and which are arrangedso that one engages one contacting surface of said wiped portion 9 of abank contact whilst the other engages the other contacting surface ofthis wiped portion, that, one wipes over one of the two tracks referredto whilst the other wipes over the other of these two tracks.

As has already been stated, FIG. 3 shows a somewhat diagrammatic viewillustrating how a composite wiper cooperates with a moulded bank unitsuch as that illustrated in FIGS. 1 and 2. The parts represented in FIG.3, which is largely in cross-section, comprise end portions 14 and 15 ofthe two constituent Wipers of a composite Wiper, a particular bankcontact 1A engaged by these two constituent wipers and included in amoulded bank unit .16, a further moulded bank unit 17 similar to thebank unit 16 and included in the same contact bank as the bank unit 16,a metal spacer 18 situated between the two bank units 16 and 17, and aclamping plate 19 and resilient pad 20 used in forming the contact bankconcerned (which will of course include other elements such as furtherbank units, further metal spacers, a further clamping plate, andclamping bolts). As will be clear from FIG. 3, when the two constituentWipers of a composite Wiper are wiping the two wiper tracks on a bankunit, the tensioned blade of one constituent wiper lies on one side ofthe supporting portion 11 of the moulded insulating material of the unitand the tensioned blade of the other constituent wiper lies on the otherside of this supporting portion. It will also be clear that, with acomposite wiper of the kind referred to, effective electrical bridingaction can be obtained when required by arranging that the contactingtip of one of the two constituent wipers wipes slightly in advance ofthe contacting tip of the other of the two constituent wipers.

It is preferred to arrange that the contacting tip of each constituentwiper of a composite wiper has the form illustrated in FIGS. 4, 5, and6. As has already been stated, FIG. 4 is a plan view of the tip portionof a constituent wiper of a composite wiper, and FIGS. 5 and 6 arerepsectively side and end views of this tip portion.

4. The advantages of the form of contacting tip illustrated in FIGS. 4,5, and 6 are that it offers an easy slope to the bank member it engageswhen entering the bank, and that it avoids engagement, and consequentwear, of the Wiper track by any sharp cutting edge.

Referring again to FiGS. 1 and 2, it should be noted that a strip 21 ofthe moulded insulating material, corresponding to, and supported in thesame way as, the strips 13 that fill the gaps between said wipedportions of the bank contacts, precedes the first bank contact in therow so as to cause the two unbroken wiper tracks to commence in advanceof this bank contact. This arrangement has the advantage that vibrationof each constituent wiper caused by the initial engagement of acomposite wiper with the bank unit has wholly or effectively died awaybefore the constituent wipers reach the first bank contact.

What I claim is:

A moulded bank unit comprising a plurality of bank contacts moulded intoinsulating material to form a row of bank contacts spaced apart from oneanother, each of said bank contacts having a tag portion protrudingclear of the moulded insulating material from a face of a main body ofthis material, a main embedded portion embedded in the main body of themoulded insulating material and having none of its surface exposed, awiped portion protruding from a further face of said main body of themoulded insulating material and having its surface partly exposed toform at least one contacting surface to permit of wiper engagement withit, and a further portion extending from said wiped portion in thedirection away from said main embedded portion, the moulded insulatingmaterial extending, in the form of strips protruding from said main bodyof this material, into the gaps between said wiped portions of said bankcontacts to fill these gaps with insulating material flush with thecontacting surfaces of said wiped portions to provide at least onesmooth and mechanically unbroken wiper track, and said strips beingsupported, at their ends remote from said main body of the mouldedinsulating material, by a supporting portion of the moulded insulatingmaterial, this supporting portion taking the form of a continuous lengthof the moulded insulating material integral with said main body and withsaid strips and interconnecting said ends of said strips and having saidfurther portions of said bank contacts embedded in it to cause it to besupported by said bank contacts.

References Cited in the tile of this patent

